Narrow Results

We carry out a computational investigation of the alkaline-earth (Ba)-based silicon and carbon oxide perovskites (BaSiO₃ and ${\text{BaCO}}_3)$ with the aim of their potential in wide-ranged applications. Exploiting the density functional theory (DFT) coded within Wien2K, we study the structural, electronic, and optical properties of these compounds. Modified Becke–Johnson (mBJ) potential, the established approach for obtaining accurate results, is employed to carry out the electronic investigation. With a simple cubic structure, we find that these materials exhibit metallic properties, as revealed by their mutually consistent band structure profiles and density of states. The valence band minima and conduction band maxima overlap at the $\mathrm{\Gamma }$ point in the band structure. We analyze the total and partial density of states to determine the proportional contributions of each atom, both in total and within individual subshells, such as the $p$- and $d$-subshells in the case of the partial density of states. In our investigation of the optical properties of these materials over the energy range of 0–14eV, we find that they effectively absorb ultraviolet and visible (UV–Vis) light. This shows that the studied compounds have potential applications in luminescence and devices requiring absorption in the UV range. BaCO₃ demonstrates more absorption spectra than the BaSiO₃ versus photon energy ranging from 1.7 to 3.1eV (visible range), suggesting that the BaCO₃ is more suitable than BaSiO₃ for applications that require UV absorption such as sunscreen, UV-blocking films, photodetectors and UV sensors and medical applications. We also find that BaCO₃ with a higher refractive index (11) compared to BaSiO₃ (4.2), is denser than BaSiO₃, resulting in a lower speed of light within the material. This suggests that BaCO₃ is more promising than BaSiO₃ for applications in eyewear. We infer that this study will guide and stimulate experimental investigations into these materials, given their potential for various applications.

In this paper, we report a density functional study of the structural, electronic and pressure-induced solid–solid phase transitions of SrTiO₃. These first-principles calculations have been performed using the full potential linearized augmented plane wave method (FP-LAPW) within the generalized gradient approximation (GGA) developed by Perdew–Burke–Ernzerhor for solids (PBEsol). The calculated structural parameters like the lattice parameters, the bulk modulus B and their pressure derivative B′ are used to analyze the relative stability and phase transitions under pressure of SrTiO₃. Calculations were done for the cubic (Pm-3m), tetragonal (I4/mcm, P4/mbm, P4mm) and orthorhombic (Cmcm, Pnma) structures where we found that the tetragonal I4/mcm phase is the most stable structure compared to the other structures at T = 0 K and P = 0 GPa. For the electronic properties calculations, the exchange and correlation effects were treated by the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential to prevent the shortcoming of the underestimation of the energy gaps in both LDA and GGA approximations. The obtained results are compared to available experimental data and to other theoretical calculations.

Very little information is available about the structural properties of III-nitride binary compounds in the rock-salt phase. We report/review a comprehensive theoretical study of structural properties of these compounds in rock-salt, zinc-blende and wurtzite phases. Calculations have been made using full-potential linearized augmented plane wave plus local orbitals (FP-L(APW+lo)) method as embodied in WIEN2k code framed within density functional theory (DFT). In this approach of calculations, local density approximation (LDA) [J. P. Perdew and Y. Wang, Phys. Rev. B45 (1992) 13244] and generalized gradient approximation (GGA) [J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett.72 (1996) 3865] have been used for exchange-correlation energy and corresponding potential. Calculated results for lattice constants, bulk modulus, its pressure derivative and cohesive energy of these compounds are consistent with the experimental results. Following these calculations, besides many new results for the rock-salt and other phases, a comprehensive review of the structural properties emerges. We also list some peculiar features of these compounds.